A structural formula is a formula that shows how the atoms in a molecule are bonded to one another, and sometimes its three-dimensional geometry. It reveals connectivity that a molecular formula cannot, which is important because molecules with the same molecular formula can differ in structure. For example, a structural formula distinguishes ethanol from dimethyl ether, though both have the formula C₂H₆O.

结构式是表示分子中原子之间如何成键(有时还包括其三维几何构型)的式子。它揭示了分子式无法表达的连接方式,这一点很重要,因为分子式相同的分子结构可能不同。例如,结构式能区分乙醇与二甲醚,尽管二者的分子式都是 C₂H₆O。